Prominin-2 is a cholesterol-binding protein associated with apical and basolateral plasmalemmal protrusions in polarized epithelial cells and released into urine |
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Authors: | Mareike Florek Nicola Bauer Peggy Janich Michaela Wilsch-Braeuninger Christine A Fargeas Anne-Marie Marzesco Gerhard Ehninger Christoph Thiele Wieland B Huttner Denis Corbeil |
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Institution: | 1.Tissue Engineering Laboratories, BIOTEC,Dresden,Germany;2.Medical Clinic and Polyclinic I,Technische Universit?t Dresden,Dresden,Germany;3.Max Planck Institute for Molecular Cell Biology and Genetics,Dresden,Germany |
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Abstract: | Prominin-2 is a pentaspan membrane glycoprotein structurally related to the cholesterol-binding protein prominin-1, which is expressed in epithelial and non-epithelial cells. Although prominin-1 expression is widespread throughout the organism, the loss of its function solely causes retinal degeneration. The finding that prominin-2 appears to be restricted to epithelial cells, such as those found in kidney tubules, raises the possibility that prominin-2 functionally substitutes prominin-1 in tissues other than the retina and provokes a search for a definition of its morphological and biochemical characteristics. Here, we have investigated, by using MDCK cells as an epithelial cell model, whether prominin-2 shares the biochemical and morphological properties of prominin-1. Interestingly, we have found that, whereas prominin-2 is not restricted to the apical domain like prominin-1 but is distributed in a non-polarized fashion between the apical and basolateral plasma membranes, it retains the main feature of prominin-1, i.e. its selective concentration in plasmalemmal protrusions; prominin-2 is confined to microvilli, cilia and other acetylated tubulin-positive protruding structures. Similar to prominin-1, prominin-2 is partly associated with detergent-resistant membranes in a cholesterol-dependent manner, suggesting its incorporation into membrane microdomains, and binds directly to plasma membrane cholesterol. Finally, prominin-2 is also associated with small membrane particles that are released into the culture media and found in a physiological fluid, i.e. urine. Together, these data show that all the characteristics of prominin-1 are shared by prominin-2, which is in agreement with a possible redundancy in their role as potential organizers of plasma membrane protrusions. |
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Keywords: | Prominin-1 (CD133) Lipid raft Microvillus Prominosome MDCK cells Mouse (C57B16) |
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